On Mon, 16 Apr 2012 20:25:06 +0000 "Myklebust, Trond" <Trond.Myklebust@xxxxxxxxxx> wrote: > On Mon, 2012-04-16 at 15:43 -0400, Jeff Layton wrote: > > On Mon, 16 Apr 2012 19:33:05 +0000 > > "Myklebust, Trond" <Trond.Myklebust@xxxxxxxxxx> wrote: > > > > > On Mon, 2012-04-16 at 13:46 -0400, Jeff Layton wrote: > > > > The question about looping indefinitely really comes down to: > > > > > > > > 1) is a persistent ESTALE in conjunction with a successful lookup a > > > > situation that we expect to be temporary. i.e. will the admin at some > > > > point be able to do something about it? If not, then there's no point > > > > in continuing to retry. Again, this is a situation that *really* should > > > > not happen if the filesystem is doing the right thing. > > > > > > > > 2) If the admin can't do anything about it, is it reasonable to expect > > > > that users can send a fatal signal to hung applications if this > > > > situation occurs. > > > > > > > > We expect that that's ok in other situations to resolve hung > > > > applications, so I'm not sure I understand why it wouldn't be > > > > acceptable here... > > > > > > There are definitely potentially persistent pathological situations that > > > the filesystem can't do anything about. If the point of origin for your > > > pathname (for instance your current directory in the case of a relative > > > pathname) is stale, then no amount of looping is going to help you to > > > recover. > > > > > > > Ok -- Peter pretty much said something similar. Retrying indefnitely > > when the lookup returns ESTALE probably won't help. I'm ok with > > basically letting the VFS continue to do what it does there already. If > > it gets an ESTALE, it tries again with LOOKUP_REVAL set and then gives > > up if that doesn't work. > > > > If however, the operation itself keeps returning ESTALE, are we OK to > > retry indefinitely assuming that we'll break out of the loop on fatal > > signals? > > > > For example, something like the v2 patch I sent a little while ago? > > > Won't something like fstatat(AT_FDCWD, "", &stat, AT_EMPTY_PATH) risk > looping forever there, or am I missing something? > To make sure I understand, that should be "shortcut" for a lookup of the cwd? So I guess the concern is that you'd do the above and get a successful lookup since you're just going to get back the cwd. At that point, you'd attempt the getattr and get ESTALE back. Then, you'd redo the lookup with LOOKUP_REVAL set -- but since we're operating on the cwd, we don't have a way to redo the lookup since we don't have a pathname that we can look up again... So yeah, I guess if you're sitting in a stale directory, something like that could loop eternally. Do you think the proposed check for fatal_signal_pending is enough to mitigate such a problem? Or do we need to limit the number of retries to address those sorts of loops? -- Jeff Layton <jlayton@xxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
